The specific functions of the core include: 1) the development and validation of survey instruments and questionnaires; 2) the development of new interview or questionnaire items; 3) enrollment of persons with rheumatic diseases and their providers; 4) training and monitoring of data collection and management staff; 5) data collection; 6) data management; and, 7) statistical and rheumatologic consulting. The Panel Study is the principal data collection activity within the Core Unit. The RA Panel Study was begun in 1982-83 when a random sample of forty Northern California rheumatologists enrolled 822 persons with RA. 203 persons with RA were enrolled in 1989 and 131 were enrolled in 1995. Since its inception, the RA Panel Study has accumulated 9,547 person-years of follow-up. In the first year of the proposed cycle of funding, another 150 persons with RA will be enrolled in the Panel Study. The RA Panel Study annual interview collects information on the signals and symptoms of the RA, co-morbidity, and a complete inventory of all health care utilized for RA and non-RA reasons. In addition, the RA Panel interview will be expanded to collect concerning decisions about childbearing and parenting for EEHSR Project 3. The Core Unit will also be responsible for the collection of history and physical exams and serologic and imaging data for the D&F study concerning bone mineral density among children with SLE.